abstract

With the popularization and development of industrial automation, the demand for controllers is increasing year by year, and the application of handling manipulator is gradually popularized, mainly in the production lines or cargo handling in the fields of automobiles, electronics, machining, food, medicine and so on. , can better save energy, improve the efficiency of transportation equipment or products, thereby reducing the limitations and shortcomings of other transportation methods and adapting to the requirements of modern economic development.

The mechanical structure of the manipulator mainly includes hydraulic steel controlled by two electromagnetic valves, which realizes the ascending and descending movement of the manipulator and the action of clamping the workpiece. Two motors with different speeds control the forward rotation and reverse rotation of the motors through two coils respectively, so as to realize the fast forward, slow forward, fast backward and slow backward movement of the car. Its action conversion is transmitted to the PLC controller through the on-off signals generated by the travel switches (SQ 1-SQ9) installed in different positions, and different signals are output through the internal program of PLC, so that the external coil is driven to control the motor or solenoid valve to generate different actions, and the accurate positioning of the manipulator can be realized. Its action process includes: descending, clamping, ascending, slow advancing, fast forwarding, slow advancing, delaying, descending, relaxing, ascending, slow retreating, fast retreating and slow retreating; Its operation modes include: return to original position, manual operation, single step, single cycle and continuous operation; To meet various operational requirements in production.

Key words: handling manipulator, programmable controller (PLC), hydraulic pressure, electromagnetic valve.

abstract

With the popularization and development of industrial automation, the demand for controllers is increasing year by year, and the application of handling robots is becoming more and more popular, mainly in the production lines or cargo transportation in the fields of automobiles, electronics, machining, food, medicine, etc., we can better save energy, improve the transportation efficiency of equipment or products, reduce the restrictions and deficiencies on other modes of transportation, and meet the requirements of modern economic development.

The mechanical structure of the manipulator includes two electromagnetic valves. The hydraulic manipulator controls the steel plate to realize the lifting motion and the workpiece clamping motion, and the rotating speeds of two different motors are positively controlled by two motor coils to realize the fast forward, slow forward, fast backward and slow backward motion of the trolley. By setting the on-off signal generated by the travel switch (SQ 1-SQ9) at different positions, the robot can realize accurate positioning by driving the external coil to control the motor or solenoid valve to generate different actions through different output signals in the PLC. Their movements include: descending, clamping, ascending, advancing slowly, fast-forwarding, advancing slowly, extending, descending, relaxing, ascending, retreating slowly, rewinding and retreating slowly; Its operations include: returning to the original position, manual operation, single step, single cycle and continuous operation; Meet the requirements of various operations and maintenance in production.

Key words: handling manipulator, programmable controller (PLC), hydraulic pressure, electromagnetic valve.

catalogue

The previous words

The first chapter is the general situation of manipulator.

1. 1 Application of handling manipulator

The application significance of 1.2 manipulator

Development of 1.3 manipulator

The third chapter is the design of PLC control system for handling manipulator.

3. 1 Structure and Action of Handling Manipulator ..........................................

3.2 Hardware design of handling manipulator system ..........................................

3.3 Control program design of handling manipulator.

1 operation panel and action description ............................................

2 input/output allocation ........................................................

3 ladder diagram design ..........................................................

The overall design of 1) ladder diagram ...................................................

2) Design of ladder diagram of each part. ...............................................

3) Draw the PLC control ladder diagram of the handling manipulator. ....................................

Conclusion.

thank you ....................................................................

references

order

Manipulator: Manipulator, also known as automatic hand and automatic hand.

An automatic operating device that can imitate some action functions of human hands and arms to grab and carry objects or operate tools according to fixed programs. It can replace people's heavy labor, realize mechanization and automation of production, operate in harmful environment and protect personal safety, so it is widely used in machinery manufacturing, metallurgy, electronics, light industry, atomic energy and other industries.

The manipulator is mainly composed of hand, motion mechanism and control system. A hand is a component used to grasp a workpiece (or tool). According to the shape, size, weight, material and operation requirements, there are various structural forms such as clamping, holding and adsorption. The motion mechanism enables the hand to complete all kinds of rotation (swing), movement or compound movement, so as to realize the specified action and change the position and posture of the caught object. The independent motion modes of the motion mechanism, such as lifting, stretching and rotating, are called the degrees of freedom of the manipulator. In order to grasp objects in any position and direction in space, six degrees of freedom are needed. Degree of freedom is the key parameter of manipulator design. The more degrees of freedom, the greater the flexibility and versatility of the manipulator, and the more complicated its structure. Generally, a special manipulator has 2 ~ 3 degrees of freedom.

The types of manipulator can be divided into hydraulic, pneumatic, electric and mechanical manipulator according to the driving mode; According to the scope of application, it can be divided into two types: special manipulator and general manipulator; According to the control mode of motion trajectory, it can be divided into point control and continuous trajectory control manipulator.

Manipulators are usually used as additional devices for machine tools or other machines, such as loading and unloading and transferring workpieces on automatic machine tools or automatic production lines, and changing tools in machining centers. And generally there is no independent control device. Some operating devices need people to operate directly, such as the master-slave manipulator used by the atomic energy department to handle dangerous goods, which is also often called manipulator. The application of manipulator in forging industry can further exert the production capacity of forging equipment and improve working conditions such as heat and fatigue.

The manipulator was first developed in America. 1958 American control company developed the first manipulator.

Chapter 1 Overview of Manipulators

1. 1 Simple application of handling manipulator

In modern industry, the mechanization and automation of production process has become a prominent theme. In the mechanical industry, production such as processing and assembly is discontinuous. Special machine tools are an effective way to realize the automation of mass production, and automatic machines such as program-controlled machine tools, CNC machine tools and machining centers are important ways to effectively solve the automation of multi-variety and small-batch production.

But besides cutting itself, there are a lot of operations such as loading, unloading, handling and assembly, which need further mechanization. Some data show that 75% of all industrial parts produced in the United States are produced in small batches; Three-quarters of the metal processing production batch is less than 50 pieces, and the actual processing time of parts on the machine tool only accounts for 5% of the production time of parts. From this, we can see the urgency of mechanization of loading and unloading, handling and other processes, and the industrial manipulator is produced to realize the automation of these processes. The manipulator can grab and place space objects, and its actions are flexible and diverse. Suitable for small and medium-sized batch automatic production with changeable production varieties, and widely used in flexible automatic production lines.

China mechanical loading and unloading robots are mainly used in the following aspects in the mechanical industry and railway departments at home and abroad:

Application of 1. in hot working

Hot working is a kind of high temperature and dangerous heavy physical labor, which has long required automation. In order to improve work efficiency and ensure workers' personal safety, it is more necessary to use a manipulator to operate, especially for large, small, low-speed and incompetent operations.

2. The application of cold working

In cold working, the manipulator is mainly used for loading and unloading and tool installation when processing diesel engine parts and shafts, plates, boxes and other parts by single machine. Then it is applied to program control, digital control and other machine tools and becomes an indispensable part of the equipment. Recently, it has been applied in processing production lines and automatic lines, and has become an important part of the connection between machine tools and equipment.

3. Disassembly, maintenance and installation

Dismantling, repairing and assembling is one of the departments with heavy manual labor in railway industrial system, which promotes the development of manipulator. At present, domestic railway factories, locomotive depots and other departments all use mechanical hands to disassemble the three-way valve, coupler tongue, brake cylinder, axle box, wheelset and asbestos removal, which reduces the labor intensity and improves the efficiency of disassembly, repair and assembly. In recent years, a universal manipulator for bus interior painting has been developed, which can be used for bus interior continuous painting to improve working conditions and improve painting quality and efficiency.

In recent years, with the increasing application of computer technology, electronic technology and sensing technology in mechanical hands, industrial manipulator has become an important factor to improve labor productivity in industrial production.

The application significance of 1.2 manipulator

In the mechanical industry, the application significance of manipulator can be summarized as follows:

1. It can improve the automation of the production process.

The application of manipulator is conducive to improving the automation of material conveying, workpiece loading and unloading, tool replacement and machine assembly, thus improving labor productivity, reducing production costs and accelerating the pace of mechanization and automation of industrial production.

2. It can improve working conditions and avoid personal accidents. Under the conditions of high temperature, high pressure, low temperature, low pressure, dust, noise, odor, radioactive or other toxic pollution and narrow working space, it is dangerous or impossible to operate directly by hand. The application of manipulator can partially or completely replace people to complete the work safely, which greatly improves the working conditions of workers. In some simple but repetitive operations, replacing human hands with mechanical hands can avoid personal accidents caused by operational fatigue or negligence.

3. It can reduce manpower and facilitate rhythmic production.

It is one aspect to reduce manpower directly by using manipulator instead of human hands, and it is another aspect to reduce manpower because the manipulator can work continuously. Therefore, at present, almost all automatic machine tools and integrated processing automatic production lines are equipped with manipulators to reduce manpower, control production rhythm more accurately and facilitate rhythmic production.

To sum up, the effective application of manipulator is the inevitable trend of the development of machinery industry. 1.3.3 general situation and development trend of manipulator

Overview of the development of 1.3 manipulator

After decades of development, the special manipulator has now entered the era marked by the universal manipulator. Due to the application and development of universal manipulator, the development of intelligent robot is promoted. The knowledge involved in intelligent robot not only includes the basic knowledge of general machinery, hydraulics and pneumatics, but also applies some electronic technology, television technology, communication technology, computing technology, radio control, bionics and prosthetic technology, so it is a new technology with strong comprehensiveness. At present, both at home and abroad attach great importance to the development of this new technology. For decades, the research and development of this technology has been very active, the design has been constantly revised, the variety has been increasing, and the application field has been expanding.

As early as 1940s, with the development of atomic energy industry, the first generation of manipulator with simulated joints appeared.

From 1950s to 1960s, universal manipulators and NC teaching and reproducing manipulators were manufactured for conveying and loading and unloading workpieces. This kind of manipulator is also called the second generation manipulator. For example, the Unimate manipulator belongs to this type.

In the 1960s and 1970s, the universal manipulator was used in the automatic production line of spot welding and stamping of automobile body, that is, the second generation manipulator entered the application stage.

In 1980s and 1990s, the assembly manipulator was in its heyday, especially in Japan.

In the 1990s, special manipulators developed greatly and were widely used in agriculture, forestry, mining, aerospace, ocean, entertainment, sports, medical care, service and military fields.

After 1990s, with the rapid development of computer technology, microelectronics technology and network technology, the manipulator technology has also diversified rapidly.

In short, the operator's current main experience is divided into three generations:

The first generation of manipulators mainly rely on manual control, which is open-loop and has no recognition ability. The improvement direction is mainly to reduce the cost and improve the accuracy; The second generation manipulator is equipped with computer control system, which has vision, touch and even hearing and thinking ability. Research and install various sensors to feed back the received information, so that the manipulator has the sensing function; The third generation manipulator can independently complete the tasks in the working process. It keeps in touch with electronic computers and television equipment, and gradually develops into an important part of flexible manufacturing system (FMS) and flexible manufacturing unit (FMC).

The development trend of 1.4 manipulator

At present, domestic industrial machinery is mainly used for machine tool processing, casting and forging, heat treatment and so on.

Performance can not meet the needs of industrial production development.

Therefore, in our country, it is mainly to gradually expand the application scope of manipulator, focusing on the development of manipulator in casting, forging and heat treatment, in order to reduce labor intensity and improve working conditions. At the same time as the application of special manipulator, the general manipulator should be developed accordingly, and the teaching manipulator, computer-controlled manipulator and combined manipulator should be developed if possible.

The moving parts of the manipulator, such as telescopic, swinging, lifting, traversing, pitching and other mechanisms, as well as clamping mechanisms suitable for different types are designed as typical universal mechanisms, so that different typical parts can be selected to form different types of manipulators according to different job requirements. It is not only convenient for design and manufacture, but also convenient for changing jobs, expanding the scope of application. At the same time, it is necessary to improve the accuracy, reduce the impact, locate accurately and give full play to the role of the manipulator. In addition, we should also vigorously study the servo type, memory reproduction type and manipulator with tactile and visual characteristics, and consider combining them with computers to gradually become a basic unit in the whole mechanical manufacturing system.

In foreign machinery manufacturing industry, industrial manipulator is widely used and develops rapidly. At present, it is mainly used in machine tool loading and unloading, die forging press, spot welding, painting and other operations. It can complete the specified operation according to the preset operating procedures, but it does not have any perceptual feedback ability and cannot cope with external changes. If there is some deviation, it will damage the parts and even the manipulator itself. Therefore, the development trend of foreign robots is to develop robots with certain intelligence, so that they can have certain perceptual ability, feedback the changes of external conditions and make corresponding changes. If the position is slightly deviated, it can be corrected and detected by itself, with emphasis on the study of visual function and tactile function.

The vision function is to install a TV camera, an optical range finder (that is, a distance sensor) and a satellite computer on the robot. When working, the TV camera turns the image of the object into a video signal, and then transmits it to the computer, so as to analyze the type, size, color and orientation of the object, and send out instructions to control the manipulator to work.

The tactile function is to install a tactile feedback control device on the robot hand. When working, the manipulator first stretches out its finger to find the workpiece, and then stretches forward to grasp the workpiece through the pressure sensitive element installed on the finger.

The grasping force of the hand can be controlled by the pressure-sensitive element installed on the inner side of the finger, so that the grasping force can be automatically adjusted. In a word, with the development of sensing technology, the assembly ability of manipulator will be further improved. By 1995, about 50% of the cars in the world will be assembled by robots.

At present, the development of manipulator is mainly to combine manipulator with flexible manufacturing system and flexible manufacturing unit, thus fundamentally changing the manual operation state of mechanical manufacturing system at present.

General situation of 1.5 PLC and its application in mechanical hands

Application and development of 1. programmable controller

Programmable controller, now generally referred to as PLC (programmable logic controller), is a general industrial automatic control device based on microprocessor and integrating computer technology, semiconductor integration technology, automatic control technology, digital technology and communication network technology. It is widely used in metallurgy, chemical industry, transportation, electric power and other fields because of its remarkable advantages, and has become one of the three pillars of modern industrial control.

Before the appearance of programmable controller, relay control was dominant in the field of industrial control. Traditional relay control has the advantages of simple structure, easy to master and low price, and is widely used in industrial production. However, the control equipment is bulky, slow, consumes more power and has fewer functions. Especially because the system is composed of hardware wiring, the wiring is more complicated. When the production process or control object changes, the original wiring control panel (cabinet) must be changed or replaced, which has poor universality and flexibility.

Application of 2.2. Programmable Logic Controller (PLC)

The application field of PLC is very extensive, and it is expanding rapidly. For the current PLC, it can be said that PLC is needed almost wherever the control system is needed. Especially in recent years, PLC has been widely used in metallurgy, machinery, petroleum, chemical industry, light industry, electric power and other industries.

According to the control type of PLC, its application can be roughly divided into the following aspects.

1). Used for logic control.

This is the most basic and widely used aspect of PLC. Replace relay control and sequence controller control with PLC. Such as machine tool electrical control, packaging machinery control, automatic elevator control, etc.

2). Used for analog control.

Through analog I/O module, PLC can realize the conversion between analog and digital, and control the analog.

3). Used for NC machining.

Modern PLC has powerful data processing function, which can be closely combined with numerical control and computer control in machining to realize digital control.

4). Used for industrial robot control.

5) Used in multi-layer distributed control system.

High-function PLC has strong communication ability, which can realize communication between PLCs, between PLC and remote I/O, and between PLC and upper computer. So as to form a multi-layer distributed control system or a factory automation network.

3. The characteristics of 3.PLC

1). High reliability and strong anti-interference ability.

PLC can work reliably in harsh environments such as electromagnetic interference, power supply voltage fluctuation, mechanical vibration and temperature change. The average time to failure of PLC is high, and the average time to failure of F 1 series PLC of Mitsubishi Corporation of Japan is as long as 300,000 h, which is incomparable to ordinary microcomputer.

2) The control system is simple in structure and universal.

Because PLC uses software programming to realize the control function, for the same control object, when the control requirements change and the function of the control system needs to be changed, it is not necessary to change the hardware equipment of PLC, only the software program needs to be changed accordingly.

three

Since 1960s, the manipulator has been recognized as a product, and its development and application are also developing. Manipulators are widely used for carrying objects, assembling, cutting and spraying dyes. Now it has been used in machinery manufacturing, metallurgy, chemical industry, electric power, mining, building materials, light industry, food, environmental protection and other industries. For example, the most typical development is that manufacturers apply this product to the health industry (automatic biochemical analyzer) in large quantities, thus realizing the demand for a large number of sample data in health inspection. However, the manipulator in the health field uses the method of adding a single enzyme reagent to the sample to develop color, and adopts the structural design of the filter, which leads to the expensive reagent and limits the development of the product market. With the development of technology, the design of manipulator really breaks the shackles of single reagent, heating and filtering. With the rapid development of society, the requirements of industrial field manipulator will become higher and higher, and its technology will become more and more mature.

Manipulator is a kind of control object often encountered in the field of industrial automatic control. Manipulators can accomplish many tasks, such as moving objects, assembling, cutting, jet dyeing and so on, and are widely used. Using PLC to control the manipulator to realize various designated working procedures can simplify the control circuit, save costs and improve labor productivity. Figure 1 is a schematic diagram of a manipulator for carrying articles.

Figure 1 Schematic diagram of manipulator for carrying objects

In the figure, the task of the manipulator is to transport the articles on the conveyor belt A to the conveyor belt B. In order to make the manipulator move accurately, limit switches SQ 1, SQ2, SQ3, SQ4 and SQ5 are installed at the limit positions of the manipulator, which respectively restrict the manipulator from grasping, turning left, turning right, rising and falling, and send out input signals of the action in place. A photoelectric switch SP is installed on the conveyor belt A to detect whether the articles on the conveyor belt A are in place. The start and stop of the manipulator are controlled by the start button SB 1 and the stop button SB2 in the figure.

Conveyor belts a and b are driven by motors. The movements of the manipulator, such as up, down, left, right, grasping and releasing, are driven by hydraulic pressure and controlled by six solenoid valves respectively.

2 Manipulator's Action Flow

Conveyor belt B is in a continuous running state and does not need PLC control.

The requirements for the sequential action of manipulator and conveyor belt C are:

1) When the start button SB 1 is pressed, the manipulator system works. First, the rising solenoid valve is energized, and the arm rises until the rising limit switch acts;

2) The left turn solenoid valve is energized, and the arm turns left until the left turn limit switch acts;

3) The descending solenoid valve is energized, and the arm descends until the descending limit switch acts;

4) Start the conveyor belt A to run, and the photoelectric switch SP detects whether there are articles sent out on the conveyor belt A. If the articles are detected, the electromagnetic valve is energized, and the manipulator grabs them until the limit switch acts;

5) The arm rises again until the rising limit switch acts again;

6) The right turn solenoid valve is energized, and the arm turns right until the right turn limit switch acts;

7) The arm descends again until the descending limit switch acts again;

8) Loosen the solenoid valve and electrify, and the manipulator will loosen the gripper. After a delay of 2 seconds, complete a handling task, and then repeat the above process.

9) When the stop button SB2 is pressed or power is cut off, the manipulator stops at the current working step, and when restarted, the manipulator continues to work according to the actions before stopping.

According to the requirements of the manipulator's sequential action, the timing diagram as shown in Figure 2 can be drawn. The action flow chart of the manipulator shown in fig. 3 can be made by the timing chart.

Fig. 2 Sequence diagram of robot Verna layout.

Fig. 3 Action flow chart of manipulator

3 PLC selection and I/O point allocation

3. 1 PLC selection

Because there are few input/output contacts in the manipulator system, the electrical control part is required to be small in size and low in cost, and the PLC can be monitored and managed by computer, so the multifunctional small C20P host produced by Omron Company of Japan is selected. The input point of this machine is 12, and the output point is 8. There are 136 auxiliary relays, 16 special function relays, 160 blocking relays, 8 temporary relays, 48 timers/counters and 64 16 bit data memories.

3.2 Number allocation of input/output points

According to the action flow chart of the manipulator shown in Figure 3, I/O point allocation of the electrical control system can be determined, as shown in Table 1.

Table 1 manipulator control I/O allocation table

According to the flow chart of fig. 3 and the I/O allocation table of table 1, the state transition diagram shown in fig. 4 can be compiled.

Fig. 4 State transition diagram of manipulator

4 Programming and program running

4. 1 Programming with Step Instruction

According to the state transition diagram in Figure 4, the step ladder diagram program is shown in Figure 5.

The function of "prohibit all outputs" in Figure 5 is to prohibit all outputs when stopping, so that the manipulator stops at the current working step; When it is restarted, it can continue to move from the previous step.

Under the condition that the state changes from HR0 10 to HR000, the normally closed contact of the locking relay is added to stop the manipulator in the middle step when the PLC is powered off or stops running. After the PLC is re-energized or put into operation again, because the locking relay HR has the function of state power-off protection, one of them is disconnected when restarting, which makes it impossible to set the HR000, so the manipulator can only continue to move from the subsequent step of the locking relay, which was set before stopping.

4.2 Program running

Press the start button SB 1 and input the point 0000 ON, then the auxiliary relay 1000 ON as the interlock condition, the interlock command IL ON, the coil between IL and ILC works normally, and the "all output prohibition" is lifted. If all normally closed contacts (see figure 1) are opened, the blocking relay HR000 is opened, the output point 0503 energizes the rising solenoid valve, and the arm rises. When the arm rises in place, the rising limit switch closes the input point 0005, the locking relay HR00 1 is turned on, the HR000 is reset, and the output point 050 1 energizes the left turn solenoid valve, and the arm turns left. ..... The next step is in place, the limit conditions are met, and the state is transferred to the next step. When the state is switched to the state of HR 008 ON, the output point 0506 energizes the release solenoid valve, the manipulator is released, and the timer TIM00 counts. When the timer reaches 2 seconds, the state shifts to HR000 again, and the program starts to loop from the first step again.

When stopping, press the stop button sb2,0001to turn off, the auxiliary relay 1000 will turn off, and the interlock command will turn off, prohibiting all output. However, the status of each locking relay is power-off protection, and the manipulator stops at the current working step. When the start button is pressed again, the interlock command opens, the output before stopping resumes, the operator continues to work, and the locking relay is opened before stopping.

5 concluding remarks

This paper introduces the design and application of C-series P-type small multifunctional PLC produced by OMRON Company in the step control of manipulator. The action principle, design requirements and program design method of the manipulator are expounded. The program introduced in this paper has been successfully applied in actual production.